Semiconductor memory device, phase change memory device, and method of fabricating the same

ABSTRACT

A phase change memory (PCM) device includes a substrate, bottom electrodes disposed in the substrate, a first dielectric layer disposed on the substrate, second dielectric layers, third dielectric layers, cup-shaped thermal electrodes, top electrodes, and PC material spacers. In the PCM device, each cup-shaped thermal electrode contacts with each bottom electrode. Second and third dielectric layers are disposed over the substrate in different directions, wherein each of the second and third dielectric layers covers a portion of the area surrounded by each cup-shaped thermal electrode, and the third dielectric layers overlay the second dielectric layers. The top electrodes are disposed on the third dielectric layers, wherein a plurality of stacked structure composed of the third dielectric layers and the top electrodes are formed thereon. The PC material spacers are formed on the sidewalls of each stacked structure and physically and electrically contact the cup-shaped thermal electrodes and the top electrodes.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 94147152, filed Dec. 29, 2005. All disclosure of the Taiwanapplication is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor memory device andmethod of fabricating the same, and more particularly, to asemiconductor memory device and phase change memory device with a smallheating area formed through a simple process, and a method offabricating the same.

2. Description of Related Art

Along with the rapid development and advanced function requirements ofportable products, nowadays a global market demand for memory isexpanding rapidly, wherein the fast development of non-volatile memoryis most remarkable. Accordingly, factories and research institutes arevigorously developing next generation memory device. Among various typesof memory devices, phase change memory (PCM) device and MagnetoresistiveRAM (MRAM) have drawn great interest.

Phase change memory is a non-volatile memory device comprising a phasechange film whose resistance changes when the crystal phase of the phasechange material changes under a thermal effect. The smaller area of thephase change film subjected to thermal effect through which the currentpasses, the smaller heating current is required for changing phase, andthe smaller the RESET/SET driving current is. Correspondingly, a smallerdrive transistor area is required, i.e. a smaller size memory unit cell.Therefore, various research are directed to the design of the size ofheating area of the phase change film, for example, disclosed in EP1339111 which was published in 2003.

However, at present, most known techniques relate to complicated methodof etching contact holes in the dielectric layer or sacrificial layerfor reducing heating area of the phase change film. When the contactholes are of a nanometer size, it would be difficult to reliably fillthe hole and yield of the phase change film would be reducedsignificantly, and the dry pre-cleaning for the contact holes beforefilm-coating becomes too complicated.

SUMMARY OF THE INVENTION

The present invention provides a phase change memory (PCM) device havingreduced heating area.

The present invention further provides a method of fabricating a smallsize PCM device, wherein the fabrication yield is substantiallyincreased.

The present invention still provides a simple method of fabricating aPCM device.

The present invention yet provides a semiconductor memory devicesuitable for a micro-size or a nano-size non-volatile memory unit cell.

The present invention provides a PCM device comprising a substrate, aplurality of bottom electrodes, a first dielectric layer, a plurality ofcup-shaped thermal electrodes, pluralities of second and thirddielectric layers, a plurality of top electrodes, and a plurality of PCmaterial spacers. The bottom electrode is formed in the substrate. Thefirst dielectric layer is formed on the substrate. The cup-shapedthermal electrodes are formed in the first dielectric layer, and bottomsof the cup-shaped thermal electrodes are connected to the bottomelectrodes. The second dielectric layers are disposed on the substratein a first direction, wherein the second dielectric layers cover aportion of the area surrounded by each cup-shaped thermal electrodes.The third dielectric layers are disposed on the substrate in a seconddirection, wherein the third dielectric layers cover a portion of thearea surrounded by the cup-shaped thermal electrodes and overlays thesecond dielectric layers. The top electrodes are disposed on the thirddielectric layers, wherein a strip of stacked structure is composed ofthe third dielectric layers and the top electrodes. The PC materialspacers are disposed on the sidewalls of the stacked structures, andphysically and electrically connected to the cup-shaped thermalelectrodes and the top electrodes.

The present invention further provides a method of fabricating a PCMdevice comprising providing a substrate having a plurality of bottomelectrodes formed thereon. Next, a first dielectric layer is formed onthe substrate, wherein a plurality of cup-shaped thermal electrodes isformed in the first dielectric layer, and wherein the bottoms of thecup-shaped thermal electrodes are connected to the bottom electrodes. Aplurality of second dielectric layers is formed on the substrate,wherein the second dielectric layers cover a portion of the areasurrounded by the cup-shaped thermal electrodes in a first direction. Aplurality of stacked structures are formed on the substrate, wherein thestacked structures cover a portion of the area surrounded by thecup-shaped thermal electrodes in a second direction, and wherein thestacked structures includes the third dielectric layers and the topelectrodes. A phase change (PC) film is formed on the substrate,covering the stacked structures and the second dielectric layers, andthen the PC material film is etched anisotropically to form PC materialspacers on the sidewalls of the stacked structures. The PC materialspacers are physically and electrically connected to the cup-shapedthermal electrode and top electrode. The PC material spacers formed onthe sidewalls of the second dielectric layers are removed.

The present invention further provides a method of fabricating a PCMcomprising providing a substrate having a plurality of bottom electrodesformed therein. A first dielectric layer is formed over the substrate,wherein a plurality of cup-shaped thermal electrodes is in the firstdielectric layer, and the bottom of the cup-shaped thermal electrodescontact the bottom electrodes. A plurality of second dielectric layersis formed over the substrate, wherein the second dielectric layers covera portion of the area surrounded by the cup-shaped thermal electrode ina first direction. The edge of each second dielectric layer is rounded.A plurality of stacked structures is formed over the substrate, and eachstacked structure covers a part of the area surrounded by eachcup-shaped thermal electrode in a second direction. Each stackedstructure is composed of a third dielectric layer and a top electrode. APC material film is formed on the substrate, covering the stackedstructures and the second dielectric layers. Next, the second dielectriclayer is anisotropically etched to form PC material spacers on thesidewalls of the stacked structures. The spacer physically andelectrically contacts the cup-shaped thermal electrodes and the topelectrodes.

The present invention also provides a semiconductor memory devicecomprising a substrate, a plurality of bottom electrodes, a firstdielectric layer, second dielectric layer, a plurality of thirddielectric layers, a plurality of cup-shaped electrodes, a pluralitystrips of top electrodes, a plurality of conductive spacers and anon-volatile memory unit cell. The bottom electrodes are formed in thesubstrate. The first dielectric layer is disposed on the substrate. Thecup-shaped electrodes are disposed in the first dielectric layer and thebottoms of the electrodes are connected to the bottom electrodes. Thesecond dielectric layers are disposed over the substrate in the firstdirection, wherein each second dielectric layer covers a portion of thearea surrounded by each cup-shaped electrode. The third dielectriclayers are disposed over substrate in the second direction, wherein eachthird dielectric layer covers a part of the area surrounded by eachcup-shaped electrode, and overlays the second dielectric layers. The topelectrodes are disposed on the third dielectric layers such that thethird dielectric layers and the top electrodes form stacked structures.The conductive spacers are disposed on the sidewalls of the stackedstructures, and are physically and electrically connected to thecup-shaped electrodes and top electrodes. The non-volatile memory unitcell is inserted between each conductive spacer and each cup-shapedelectrode.

The present invention further provides a structure with two “crossed”electrode spacers, which include a bottom electrode spacer and a topelectrode spacer. The bottom electrode spacer is disposed over asubstrate in a first direction and the top electrode spacer is crossedover the bottom electrode spacer in a second direction.

The present invention employs spacers comprised of phase change materialas the contact hole structures of the thermal electrodes so the size ofcontact area between the phase change material and the thermal electrodein PCM device is smaller than that formed by a photolithography process,and is smaller than that of “surface contact structure”. Moreover, theprocess of the present invention is simpler than the conventionalprocess. Furthermore, problems caused by the misalignment of the phasechange material and the contact holes of the top electrodes can beeffectively avoided. In the process provided by the present invention,the difficulty of filling the holes due to the size of the holes beingtoo small, or the difficulty of plasma gas entering into the holes whenthe top portions of the film on sidewalls are jointed may be effectivelyavoided. Furthermore, when the planarization of the PC material film isdeveloped successfully, the cross spacer structure of the presentinvention is not limited to application in the phase change memory, butcan also be applied in a 3D-NVM structure.

In order to the make aforementioned and other objects, features andadvantages of the present invention comprehensible, a preferredembodiment accompanied with figures are described in detail below.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1G are views illustrating the process steps of fabricating aphase change memory (PCM) device according to a preferred embodiment ofthe present invention.

FIGS. 2A to 2E are views illustrating the process steps of fabricating aPCM device according to a preferred embodiment of the present invention.

FIG. 3 is a simple view illustrating the structure according to a aspectof the present invention.

DESCRIPTION OF EMBODIMENTS

FIGS. 1A to 1G are views illustrating the process steps of fabricating aphase change memory (PCM) device according to a preferred embodiment ofthe present invention.

Referring to FIG. 1A, Part (1) is a top view of the device, and Part (2)is a sectional view along line II-II of Part (1). First, a substrate 100having a plurality of bottom electrodes 102 formed therein is provided.Next, a first dielectric layer 112 is disposed over the substrate, forexample, having a first oxide layer 106 comprising a plurality ofopenings 104 formed therein, wherein the openings 104 exposes the bottomelectrodes 102. The aperture r of each opening 104 corresponds to thethickness of the subsequently formed PC material spacers, which will bedescribed in detail later.

Referring to FIG. 1B, Part (1) is a top view of the device, and Part (2)is a sectional view along the line II-II of Part (1). A thermalelectrode material is formed over the substrate 100, wherein the thermalelectrode material covers the first oxide layer 106, the inner surfacesof the openings 104 and the bottom electrodes 102. A second oxide layer110 is formed over the thermal electrode material to fill the openings104. A planarization process is performed to remove portions of thesecond oxide layer 110 and the thermal electrode material disposedoutside the openings 104, where the remaining thermal electrode materialforms cup-shaped thermal electrodes 108. The thermal electrode materialcomprises, for example, transition or refractory metal nitrides such asTiN or TaN, W, nitrided metal silicide, polysilicon, amorphous siliconor a metal silicide, and the thickness thereof is less than 20 nm. Thebottoms of the cup-shaped thermal electrodes 108 contact the bottomelectrodes 102. The first oxide layer 106 and the second oxide layer 110together form the first dielectric layer 112. It should be noted thatthe first dielectric layer 112 is not limited to only oxide layers, anyother suitable dielectric material may also be utilized.

Referring to FIG. 1C, Part (1) is a top view of the device, the secondview is a sectional view along the line II-II of Part (1), and Part (3)is a sectional view along line III-III of Part (1). A plurality ofsecond dielectric layers 114 is formed over the substrate 100, whereineach second dielectric layer 114 covers a portion of the area surroundedby each cup-shaped thermal electrode 108 in a first direction. Thethickness of the second dielectric layer 114 is, for example, 60 nm. Thestep of forming the second dielectric layers 114 comprises, for example,forming a nitride film on the substrate 100 first, and then performing aphotolithography and etching process to form the second dielectriclayers 114 in the first direction.

Referring to FIG. 1D, Part (1) is a top view of the device, and Part (2)is a sectional view along the line II-II of Part (1). A plurality ofstacked structures 116 is formed over the substrate 100, and each stripof stacked structure 116 covers a portion of the area surrounded by eachcup-shaped thermal electrode 108 in a second direction. A gap with awidth d is particularly formed between the stacked structure 116 and theinner side of the cup-shaped thermal electrode 108 so as to prevent theincrease in the contact surface area between the subsequently formed PCmaterial spacers and the cup-shaped thermal electrode 108. Moreover, thefirst direction is different from the second direction, for example, thefirst direction may be perpendicular to the second direction as shown inthis FIG. 1D. The step of forming the stacked structure 116 includes,for example, sequentially forming a third dielectric layer 118 and a topelectrode 120 over the substrate 100, and then performing aphotolithography and etching process. The top electrode 120 comprises,for example, TiW, transition or refractory metal nitrides such as TiN orTaN, Al, Cu/TaN, nitrided metal silicide, polisilicon, amorphous siliconor a metal silicide or any other suitable conductive material, thethickness of the third dielectric layer 118 is, for example, 100 nm, andthe thickness of the top electrode 120 is, for example, 100 nm. In anexample, if the design of the mask and the setting of the stepper allow,the mask for forming the stacked structure 116 and the mask for formingthe second dielectric layer 114 can be the same, but rotated 90° forexposure.

Referring to FIG. 1E, Part (1) is a top view of the device, and Part (2)is a sectional view along the line II-II of Part (1). A PC material film122 is formed on the substrate 100 to cover the stacked structures 116and the second dielectric layers 114.

Referring to FIG. 1F, Part (1) is a top view of the device, Part (2) isa sectional view along the line II-II of Part (1), and Part (3) is asectional view along the line III-III of Part (1). The PC material film122 is anisotropically etched (as shown in FIG. 1E), to form PC materialspacers 122 a on the sidewalls of the stacked structures 116. The PCmaterial spacers 122 a contact the cup-shaped thermal electrodes 108 (asshown in Part (1)). However, as the second dielectric layers 114 havevertical sidewalls, the PC material spacers 122 a are also located onthe sidewalls of the second dielectric layers 114 (as shown in Part(3)).

Referring to FIG. 1G, Part (1) is a top view of the device, and Part(2), Part (3), and Part (4) are sectional views along the line II-II,line III-III, and line IV-IV of Part (1) respectively. The PC materialspacers 122 a are over-etched to remove the PC material film on thesidewalls of the second dielectric layer 114. The time of over-etchingthe PC material spacers 122 a is, for example, the same as that orlonger than that of etching step used for reducing the thickness of thePC material spacers 122 a. When the aperture r of each opening 104(referring to FIG. 1A) is 0.2 μm, the thickness of the PC materialspacers 122 a is between 20-50 nm (the value is determined by a maximumoverlay error tolerance of the various lithographic steppers, andgenerally follows a principle of “a half of the thickness of the PCmaterial spacers plus the maximum overlay error tolerance is equal to ahalf of the width of the area surrounded by each cup-shaped thermalelectrode”). Furthermore, if the thickness of the PC material spacers122 a reaches 100 nm, the aperture r is accordingly increased.

It can be seen from FIG. G that the PCM device of the present inventionemploys the PC material spacers 122 a as contacts 124 of the entiredevice, and therefore, the contact area between the PC material spacers122 a and the thermal electrode 108 can be smaller than that fabricatedusing a photolithography process. Thus, fabrication of the smallestcontact area may be realized.

FIGS. 2A to 2E are views illustrating the process steps of fabricating aPCM device according to another preferred embodiment of the presentinvention, wherein means same or similar to the above embodiment areindicated by the same component symbols or numerals of FIGS. 1A to 1G.

Referring to FIG. 2A, Part (1) is a top view of the device, Part (2) isa sectional view along a line II-II of Part (1). The process stepsaccording to this embodiment of the present invention are the same asthose described above with reference to FIGS. 1A to 1B. A substrate 100having a plurality of bottom electrodes 102 formed therein is provided.Next, a first dielectric layer 112 comprising cup-shaped thermalelectrodes 108 formed therein is provided over the substrate 100,wherein the bottom of each cup-shaped thermal electrode 108 contactswith each bottom electrode 102.

Referring to FIG. 2B, Part (1) is a top view of the device, and Part (2)is a sectional view along the line II-II of Part (1). A plurality ofsecond dielectric layers 114 is formed over the substrate 100, whereineach second dielectric layer 114 covers a portion of the area surroundedby each cup-shaped thermal electrode 108 in a first direction.

Referring to FIG. 2C, it is a sectional view of a subsequent processalong the line III-III of Part (1) of FIG. 2B. Edges 200 of each seconddielectric layer 114 (referring to FIG. 2B) are rounded, so as to formrounded second dielectric layers 114 a. The method of forming roundedsecond dielectric layers comprises, for example, a performing a cleaningstep using inductively coupled plasma-Ar (ICP-Ar), or an isotropic(partly or fully) dry etching process, or a wet etching process.

Referring to FIG. 2D, Part (1) is a top view of the device, and Part(2), Part (3), and Part (4) are sectional views along the line II-II,line III-III, and line IV-IV of Part (1) respectively. A plurality ofstacked structures 116 is formed over the substrate 100, wherein eachstacked structure 116 covers a portion of the area surrounded by eachcup-shaped thermal electrode 108 in a second direction. The stackedstructures 116 includes the third dielectric layers 118 and the topelectrodes 120. As such, only a photolithography process is required forfabricating the stacked structures. The third dielectric layers and thetop electrodes have self-aligned linewidths and sidewalls. A PC materialfilm 122 is formed over the substrate 100 to cover the stackedstructures 116 and the rounded second dielectric layers 114 a.

Referring to FIG. 2E, Part (1) is a top view of the device, Part (2),Part (3), and Part (4) are sectional views along the line II-II, lineIII-III, and line IV-IV of Part (1) respectively. The PC material film122 (as shown in FIG. 2D) is anisotropically etched to form PC materialspacers 122 a on the sidewalls of the stacked structure 116, whereineach PC material spacer 122 a contacts with each cup-shaped thermalelectrode 108. It should be noted that due to the shape of the edges 200of the rounded second dielectric layers 114 a, PC material spacers 122 aare not formed on the sidewalls of the second dielectric layers 114 a.

Besides, the present invention can be applied in other semiconductormemory devices. For example, in the above embodiment of FIG. 2E, if thematerial of the PC material spacers 122 a is changed to a conductivematerial, a non-volatile memory unit cell can be formed between theconductive spacer and each cup-shaped electrode. For example, thecup-shaped electrodes may be comprised of TiW, transition or refractorymetal nitrides such as TiN or TaN, Al, Cu/TaN, polysilicon, amorphoussilicon, PC materials, nitrided metal silicide or a metal silicide, andthe conductive spacer may also be comprised of TiW, transition orrefractory metal nitrides such as TiN or TaN, Al, Cu/TaN, polysilicon,amorphous silicon, PC materials, nitrided metal silicide or a metalsilicide. The non-volatile memory unit cell may be a magnetic tunneljunction (MTJ) unit cell of the MRAM, an anti-fuse cell of the Mask ROMor the programmable ROM (PROM), a Resistance RAM (RRAM) unit cell, or a3D-NVM unit cell. Moreover, the first and third dielectric layers maycomprise silicon oxide, and the second dielectric layer may comprisenitride.

Additionally, FIG. 3 is a simple view illustrating the structureaccording to a aspect of the present invention.

Referring to FIG. 3, Part (1) is a top view of the structure, Part (2)and Part (3) are sectional views along the line II-II and line III-IIIof Part (1) respectively. A structure 300 at least includes two“crossed” electrode spacers which includes a bottom electrode spacer 302and a top electrode spacer 304. The bottom electrode spacer 302 isdisposed over a substrate 301 in a first direction, and the topelectrode spacer 304 is crossed over the bottom electrode spacer 302 ina second direction. The bottom and top electrode spacers 302 and 304 maybe optionally planarized by chemical mechanical polishing (CMP), andthus flat top surfaces (dotted line 302 a and 304 a) are formed as shownin Part (2) and Part (3).

In FIG. 3, the bottom electrode spacer 302 is a heating electrode suchas TiN, or a metal spacer, or a semiconductor spacer such as poly-Si oramorphous Si, or a PC material spacer for example. Moreover, the topelectrode spacer 304 is a metal spacer, or a semiconductor spacer suchas poly-Si or amorphous Si, or a PC material spacer, for example.Furthermore, the bottom electrode spacer 302 further comprises a portionof a cup-shaped metal electrode, a portion of ring-shaped metal spacerelectrode or a portion of a line-shaped metal spacer electrode. Thiskind of structure 300 can be used as the top and bottom electrodes of anMTJ of the MRAM, an Anti-Fuse of the PROM or the Mask ROM, a unit cellof the RRAM, or the like, and other equivalent non-volatile memory unitcells.

In summary, the present invention has the following characteristics.

1. In the structure of the present invention, the contact area betweenthe PC material spacers and the cup-shaped thermal electrodes is smallerthan that formed employing a photolithography process, wherein bycontrolling the area of the thickness of the PC material spacers and thecup shaped thermal electrode, the contact area can be rendered smallerthan that of the “surface contact structure”.

2. The process of the present invention is comparatively simpler thanthe conventional technique.

3. The present invention defines the contact area with the cup-shapedthermal electrodes by etching the spacers, thus completing the contactof the top electrodes, and thereby define the contact-hole structures ofthe present invention. Therefore, problems of current flow caused due tothe misalignment between the phase change material and the contact holesof the top electrodes may be effectively avoided.

4. The structure of the present invention comprises a single contacthole.

5. The process of the present invention does not require filling thephase change material film in nano-sized contact holes, and thereforethe difficulty of filling the nano-sized contact holes, or thedifficulty of the plasma gas entering the nano-sized contact holes whenthe top of the films on sidewalls at two sides are jointed may beeffectively avoided.

6. If the planarization process of the PC material film can successfullyimplemented in the future, the structure of the present invention may beapplied in the 3D-NVM.

7. The cross spacer structure of the present invention is not limited toapplication in phase change memory. For example, a portion of the PCmaterial spacers may be replaced with a conductive material such as TiNto serve as the top electrodes, non-volatile memory unit cells can beformed at the intersection of two crossed TiN's. Therefore, the physicaland electrical contact between the non-volatile memory unit cell ofnano-size and the top and bottom electrodes can be achieved more easilythan the physical and electrical contact between the memory unit with anordinary contact hole and the top and bottom electrodes. It can beeasily understood from the lithographic overlay error. The non-volatilememory unit cell described herein can be an MTJ of the MRAM, anAnti-Fuse of the PROM or the Mask ROM, a unit cell of the RRAM, or thelike, and other equivalent non-volatile memory unit cells can also beused.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A phase change memory (PCM) device, comprising: asubstrate; a plurality of bottom electrodes, formed in the substrate; afirst dielectric layer, disposed over the substrate; a plurality ofcup-shaped thermal electrodes, disposed in the first dielectric layer,wherein each bottom of the cup-shaped thermal electrodes contacts one ofthe bottom electrodes; a plurality of second dielectric layers, disposedover the substrate in a first direction, wherein each of the seconddielectric layers covers a portion of the area surrounded by each of thecup-shaped thermal electrodes; a plurality of third dielectric layers,disposed over the substrate in a second direction, wherein each of thethird dielectric layers covers a portion of the area surrounded by eachof the cup-shaped thermal electrodes, and overlays the second dielectriclayers; a plurality of top electrodes, disposed over the thirddielectric layers so that a plurality of stacked structures includingthe third dielectric layers and the top electrodes are formed over thesubstrate; and a plurality of phase change (PC) material spacers,disposed on sidewalls of the stacked structures, wherein the PC materialspacers physically and electrically contact the cup-shaped thermalelectrodes and the top electrodes.
 2. The PCM device as claimed in claim1, wherein the material of the cup-shaped thermal electrodes comprisestransition or refractory metal nitrides, W, nitrided metal silicide,polysilicon, amorphous silicon or a metal silicide.
 3. The PCM device asclaimed in claim 1, wherein the material of the top electrodes compriseTiW, transition or refractory metal nitrides, Al, Cu/TaN , nitridedmetal silicide, polisilicon, amorphous silicon or a metal silicide. 4.The PCM device as claimed in claim 1, wherein the first dielectriclayers and the third dielectric layers are the same material other thansilicon dioxide, and the second dielectric layers are a dielectricmaterial with an etching selectivity with the first and third dielectriclayers.
 5. A method of fabricating a phase change memory (PCM) device,comprising: providing a substrate having a plurality of bottomelectrodes formed therein; forming a first dielectric layer having aplurality of cup-shaped thermal electrodes over the substrate, whereineach bottom of the cup-shaped thermal electrodes contacts one of thebottom electrodes; forming a plurality of second dielectric layers onthe substrate, wherein each of the second dielectric layers covers aportion of the area surrounded by each of the cup-shaped thermalelectrodes in a first direction; forming a plurality of stackedstructures on the substrate, wherein each of the stacked structurescovers a portions of the area surrounded by each of the cup-shapedthermal electrodes in a second direction, and wherein each of thestacked structures includes a third dielectric layer and a topelectrode; forming a PC material film over the substrate, covering thestacked structures and the second dielectric layers; anisotropicallyetching the PC material film to form a plurality of PC material spacerson sidewalls of the stacked structures, wherein each of the PC materialspacers physically and electrically contacts each of the cup-shapedthermal electrodes and top electrodes, and wherein the PC materialspacers comprise phase change material; and over-etching the PC materialspacers to remove the PC material film on the sidewalls of the seconddielectric layers.
 6. The method of fabricating a PCM device as claimedin claim 5, wherein the step of forming the second dielectric layers onthe substrate comprises: forming a nitride film over the substrate; andcarrying out a photolithography and an etching process to form thesecond dielectric layers in the first direction.
 7. The method offabricating a PCM device as claimed in claim 5, wherein the step offorming the stacked structures on the substrate comprises: sequentiallyforming the third dielectric layer and the top electrode on thesubstrate; and performing a photolithography and an etching process toform the stacked structures in the second direction.
 8. The method offabricating a PCM device as claimed in claim 5, wherein a time ofover-etching the PC material spacers is the same as that for etching thePC material spacers for reducing thickness thereof.
 9. The method offabricating a PCM device as claimed in claim 5, wherein the step offorming the first dielectric layer having a plurality of cup-shapedthermal electrodes over the substrate comprises: forming a first oxidelayer comprising a plurality of openings over the substrate, wherein theopenings expose the bottom electrodes; forming a thermal electrodematerial layer over the substrate to cover the first oxide layer, theinner surfaces of the opening and the bottom electrodes; forming asecond oxide layer to fill the openings; and planarizing the secondoxide layer to remove portions of the second oxide layer and the thermalelectrode material layer disposed outside the openings.
 10. A method offabricating a phase change memory (PCM) device, comprising: providing asubstrate having a plurality of bottom electrodes formed therein;forming a first dielectric layer comprising a plurality of cup-shapedthermal electrodes over the substrate, wherein each bottom of thecup-shaped thermal electrodes contacts one of the bottom electrodes;forming a plurality of second dielectric layers over the substrate,wherein each of the second dielectric layers covers a portion of thearea surrounded by each of the cup-shaped thermal electrodes in a firstdirection; performing a treatment process for rounding edges of each ofthe second dielectric layers; forming a plurality of stacked structuresover the substrate, wherein each of the stacked structures covers aportion of the area surrounded by each of the cup-shaped thermalelectrodes in a second direction, and each of the stacked structures iscomposed of a third dielectric layer and a top electrode; forming a PCmaterial film over the substrate to cover the stacked structures and thesecond dielectric layers; and anisotropically etching the PC materialfilm to form a plurality of PC material spacers on sidewalls of thestacked structures, wherein the PC material spacers physically andelectrically contact the cup-shaped thermal electrodes and the topelectrodes.
 11. The method of fabricating a PCM device as claimed inclaim 10, wherein the treatment process to round the edges of each ofthe second dielectric layers comprises using a cleaning step usinginductively coupled plasma-Ar, an isotropic dry etching process or a wetetching process.
 12. The method of fabricating a PCM device as claimedin claim 10, wherein the step of forming the second dielectric layers onthe substrate comprises: forming a nitride film over the substrate; andperforming a photolithography and etching process to form the seconddielectric layers in the first direction.
 13. The method of fabricatinga PCM device as claimed in claim 10, wherein the step of forming thestacked structures on the substrate comprises: sequentially forming athird dielectric layer and a top electrode over the substrate; andperforming a photolithography and etching process to form the stackedstructures in the second direction.
 14. The method of fabricating a PCMdevice as claimed in claim 10, wherein the step of forming the firstdielectric layer over the substrate comprises: forming a first oxidelayer comprising a plurality of openings formed therein over thesubstrate, wherein the openings expose the bottom electrodes; forming athermal electrode material over the substrate covering the first oxidelayer, the openings, and the bottom electrodes; filling the openingsusing a second oxide layer; and planarizing the second oxide layer toremove portions of the second oxide layer and the thermal electrodematerial disposed outside the openings.
 15. A semiconductor memorydevice, comprising: a substrate; a plurality of bottom electrodes,formed in the substrate; a first dielectric layer, disposed on thesubstrate; a plurality of cup-shaped electrodes, disposed in the firstdielectric layer, wherein each bottom of the cup-shaped electrodescontacts one of the bottom electrodes; a plurality of second dielectriclayers, disposed over the substrate in a first direction, wherein eachof the second dielectric layers covers a portion of the area surroundedby each of the cup-shaped electrodes; a plurality of third dielectriclayers, disposed over the substrate in a second direction, wherein thethird dielectric layers covers a portion of the area surrounded by thecup-shaped electrodes, and overlays the second dielectric layers; aplurality of top electrodes, disposed over the third dielectric layers,wherein a plurality of stacked structure composed the third dielectriclayers and the top electrodes is formed; a plurality of conductivespacers, disposed on sidewall of the stacked structure, wherein theconductive spacers physically and electrically contact the cup-shapedelectrodes and top electrodes; and a non-volatile memory unit cell,formed between each of the conductive spacers and each of the cup-shapedelectrodes.
 16. The semiconductor memory device as claimed in claim 15,wherein the material of the cup-shaped electrodes comprises TiW,transition or refractory metal nitrides, Al, Cu/TaN, polysilicon,amorphous silicon, PC materials, nitrided metal silicide or a metalsilicide.
 17. The semiconductor memory device as claimed in claim 15,wherein the material of the conductive material spacers comprises TiW,transition or refractory metal nitrides, Al, Cu/TaN, polysilicon,amorphous silicon, PC materials, nitrided metal silicide or a metalsilicide.
 18. The semiconductor memory device as claimed in claim 15,wherein the first and third dielectric layers are the same materialother than silicon dioxide, and the second dielectric layers are adielectric material with an etching selectivity with the first and thirddielectric layers.
 19. The semiconductor memory device as claimed inclaim 15, wherein the non-volatile memory unit cell comprises an MTJunit cell of a MRAM, an anti-fuse cell of a Mask ROM or a PROM, or aunit cell of a RRAM.
 20. A structure, comprising: a bottom electrodespacer, disposed over a substrate in a first direction; and a topelectrode spacer, crossed over the bottom electrode spacer in a seconddirection.
 21. The structure as claimed in claim 20, wherein the topelectrode spacer further comprises a portion of ring-shaped metal spacerelectrode or a portion of a line-shaped metal spacer electrode.
 22. Thestructure as claimed in claim 20, wherein the bottom electrode spacerfurther comprises a portion of a cup-shaped metal electrode, a portionof ring-shaped metal spacer electrode or a portion of a line-shapedmetal spacer electrode.